1. Field of the Invention
The invention relates to a fiber laser apparatus and a method of detecting a failure of the fiber laser apparatus.
2. Background of the Invention
Recently, there is an improvement in an intensity of fiber laser apparatuses that utilize an optical fiber as an oscillating device or an amplifying device and such fiber laser apparatuses are finding a broader use as machining laser apparatuses.
With such a fiber laser apparatus, a phenomenon referred to as a so-called “fiber fuse” may occur that causes an irreversible damage in a core of an optical fiber towards a light source. When such a fiber fuse occurs, there will be an increased financial loss since the fiber fuse breaks a fiber component that exists before reaching the light source.
In the related art, such a method of detecting a fiber fuse may be a method as disclosed in Japanese Laid-Open Patent Publication No. 2003-227776 in which light and a temperature of a fiber fuse are detected or a method as disclosed in International Publication No. WO2004/088881 in which pump light is split and observed, and determining that, in a case where a pump light intensity has decreased, a fiber fuse has occurred.
In order to detect light of a fiber fuse itself or a temperature change caused thereby as disclosed in Japanese Laid-Open Patent Publication No. 2003-227776, it is necessary to provide a monitoring mechanism at every possible position whereto the fiber fuse may propagate and thus an increased cost is required. When the monitoring mechanisms are provided at a fewer number of positions, there is a drawback of an increased repair cost, since it requires time to stop the laser and damaging of an optical element continues until the laser is stopped.
A method of sensing a pump light disclosed in International Publication No. WO2004/088881 has a following drawback. In a fiber laser apparatus constituted using a DCF (Double Clad Fiber), the pump light propagates in a clad. Accordingly, even if a fiber fuse is produced that damages the core only, the pump light may continue to propagate. Therefore, there is a possibility that an occurrence of a fiber fuse cannot be detected.